Design of Modern Radio 
Receiving Sets 

By M.. B. Sleeper 


GIM BEL BROTHERS 

RADIO HEADQUARTERS 

NEW YORK 


Radio and Model Engineering Series 

No. 1 

Price Fifty Cents 









































Copyright 1922 

BY 

M. B. Sleeper 



PUBLISHED BY 

The General Apparatus Company, Inc. 
88 Park Place 

NEW YORK 

©CIA 677511 


Design of 

Modern Radio Receiving Sets 

By M. B. Sleeper 


Showing the construction of instruments so simple 
that they can be assembled in the “kitchen table 
workshop/’ yet so designed that they give the 
appearance and results of commercial equipment. 


Second Edition 










TABLE OF CONTENTS 


A Loose Coupler That Does What Is Expected of It 

A design is given for a loose coupler with which primary and secondary windings 
can be used to give a wavelength range, with an ordinary 0.0003 mfd. antenna, 
of 169 to 1,066 meters or 179 to 2,665 meters. 

Single Circuit Audion Receiver 

Compact and convenient, this set is admirably adapted for general reception 
on wavelengths from 150 to 3,200 meters, tuning in amateur, phone, commer¬ 
cial, and time signal transmitters. 

A Real Radio Receiving Equipment 

Of all apparatus described in Radio and Model Engineering this 150 to 
2,600-meter regenerative receiver has been, and still is, the most popular. 
Criticisms have been made that the tuning is somewhat broad, and that some 
loss of efficiency is experienced below 300 meters, but for phone reception and 
commercial stations up to time signals it is hardly surpassed by the most 
elaborate variometer sets. 

A Real Radio Receiving Equipment 

The detector and 2-step amplifier described is primarily designed to be used 
with the 150 to 2,600 meter regenerative receiver, tho it is equally good for any 
type receiving set. In fact, it can be wired to a crystal receiver, such as the 
Areola, Jr., when loud signals are required. ...... 

Simple Crystal Receiver for Phone Reception 

Here is an excellent crystal receiver, costing less than five dollars to assemble, 
which, with a single wire antenna 100 ft. long and 30 ft. high, will receive 
phone broadcasts up to 15 or even 20 miles. 

Radio Frequency Amplification at 200 Meters 

The simplest type of radio frequency amplifier is described, embodied in a set 
that gives astonishingly sharp tuning. Suitable for regular 200-meter traffic 
the set offers interesting possibilities for experimenting. By slightly increasing 
the number of turns on the coils phone stations can be received. 

12,000 to 20,000 Meter Receiver 

European stations come in with surprising strength when an audion detector 
is used in conjunction with this instrument. Simplicity of control, without 
sacrifice of efficiency, is a strong point in its favor. It is an interesting set to 
operate, and opens a new field for the man who has only worked on short waves. 

150 to 600 Meter Regenerative Receiver 

Another special success has been scored by this equipment. For relay work 
on 200 meters it is unexcelled, both in the matter of signal strength and tuning. 
The man who has experienced interference while receiving phone broadcasts or 
is troubled with weak signals can promise himself a new experience when 
operating this outfit. . . 

Some Common Radio Problems 

A few answers and remedies are given for perplexities that are frequently 
met by the novice and experimenter. 

Ideas for the Shop and Laboratory 

Suggestions are given for an oscillating wavemeter, inductance standards, and 
a phone bob, handy pieces of apparatus for the man who is doing experimental 
work. 

Lists of Parts and Prices 

To describe the construction of an instrument for which parts cannot be ob¬ 
tained is only an aggravation. Consequently, complete lists of parts and prices 
are given for G. A. Standardized Supplies of which the equipment can be built. . 


Page 9 


Page 13 


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Page 46 






















I 




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PREFACE 


So popular were the articles which appeared in Radio 
and Model Engineering from the first issue, in 
May, 1921, to the last number of the year that, in 
response to a demand which has entirely exhausted 
the supply of back numbers, the material on receiving 
sets has been reprinted in book form. 

The reason for this demand is probably the care and 
sincerity with which the articles were prepared. A 
feeling of confidence seems to be created by the manner 
in which the data is presented, and is justified by the 
results obtained when the work has been carried out 
carefully. Those who are not familiar with radio 
construction work may be reminded, however, that 
the best directions are not proof against faulty work¬ 
manship. 

An unusual feature of this book is the list of parts 
and prices to accompany the instruments described, 
giving the experimenter a source of supply for parts 
required. 

Assistance of great value was rendered, in the prepara¬ 
tion of this data, by Mr. W. H. Bullock, whose exper¬ 
ience in radio design contributed greatly toward sim¬ 
plifying mechanical and electrical construction. 

M. B. Sleeper 




A Loose Coupler That Does What Is Expected of It 


9 


A Loose Coupler That Does What 
Is Expected Of It. 

Homemade loose couplers seldom meet the expectations of the experimenter in the 
matter of wavelength range. Here are some ideas which cannot go away. 


M OST Experimenters are 
over th e idea that the 
and Wave- bigger the antenna the louder 
length. t h e signals. For all-round 
work a single wire 100 ft. long, averag¬ 
ing 30 ft. high, is the thing. Such an 
antenna is best suited for wavelengths 
from 200 to 2,500 meters. 

The wavelength of any circuit depends 
on the amount of capacity and inductance 
in that circuit. Since the antenna pro¬ 
vides the capacity of the primary circuit, 
the inductance of the primary must be 
of such a size as to give, with the an¬ 
tenna capacity, the wavelength range 
required. 

The usual loose coupler, bought or 
homemade, has enough taps on the sec¬ 
ondary, to look reasonable. But, usually, 
there is very little reason connected with 
it. Unless a condenser is used in the 
secondary circuit, sharp tuning cannot 
be obtained, and if a condenser is used, 
the taps should be so arranged, that, 
with a specified condenser, the wave¬ 
length with maximum capacity at one 
tap will be slightly higher than the 
wavelength at minimum capacity on the 
next tap. This provides an overlap. 

A PARTICULAR disad¬ 
vantage of the ordinary 
Coupler?° Se loose coupler is that the con¬ 
trols are not of the rotary 
type, mounted on the panel. In the in¬ 
strument illustrated in Fig. 1, however, 
the primary and secondary coils are 
mounted at right angles to give zero 
coupling. Coupling is provided by the 
primary coupling coil which rotates in¬ 
side the secondary. 

Two switches at the left control the 
primary inductance, one for small steps 
and one for large steps, and a single 
switch, on the right regulates, the sec¬ 
ondary coil. No primary condenser is 
needed, but a G. A. STD variable con¬ 
denser, 0.0008 mfd., is required for fine 
tuning in the secondary circuit. Con¬ 
nections for this instrument are the same 
as for an ordinary loose coupler. Speci¬ 


fications are given for two sets of coils, 
one for 200 to 1,000 meters, and one set 
for 200 to 2,500 meters, according to the 
requirements of the builder. 


IG. 2 shows the front 
Laying panel, rear connection 

Panel! he panel, primary coil at the left, 
and secondary coil at the 
right, variometer shaft contact spring, 
and coil mounting post, with a diagram 
of connections in the lower corner. It 
is hard to make the average Experi¬ 
menter understand that his combination 
square, dividers, scriber and center punch 
are his best friends on a job of this sort. 
Since the drawings have been laid out 
exactly to scale and reduced one-half, to 
determine a dimension, it is only neces¬ 
sary to set the dividers on the drawing 
and lay off that distance twice on the 
panel. In this way fine work can be 
done easily. 


Tj 1 IG. 3 shows the long and 
rr U T „ -*■ short wave coils. The 

ductances same size tubes, ot the di¬ 

mensions given in Fig. 2 are 
used for all the coils. For the secondary, 
either long or short wave, a considerable 
portion of the tube is not wound. This 
is done so that the screws which hold 
the coil mounting pillars to the panel 
will be out of sight under the coupling 
dial. 

SHORT WAVE PRIMARY: The short 
wave primary coil is wound with No. 24 
S. S. C. wire on a G-A-Lite tube 3% ins. 
long and 3^4 ins. in diameter. Starting 
5/16 ins. from the left hand end, taps 
are taken off at the following turns: 0, 
2, 4, 6, 8, 10, 20, 30, 40, 50, 60, 70, 80, 90, 
100 and 110. The first five are con¬ 
nected to the upper switch, and balance 
to the lower. An extra switch point is 
provided at each extremity so that the 
lever will not slip off. The full coil has 
an inductance of 1.0 millihenry which, 
with an antenna of 0.0003 mfd., gives a 
maximum wavelength of 1,032 meters. 
SHORT WAVE SECONDARY: The 
same tube and wire are used for this coil. 






10 


Radio and Model Engineering 


Start the winding J4-in. above the center 
of the shaft hole, and take off taps at 
the 24th turn, and the 62nd, which is the 
end of the coil. The inductance with the 
first tap is 0.08 millihenry and 0.40 milli- 


hand end, taking off taps from the fol¬ 
lowing turns: 0, 6, 9, 12, 15, 18, 21, 39, 57, 
75, 93, 111, 129, 147, 165, 183, 201, 219, 
237, 255 and 273. The first six go to the 
upper switch, and the balance to the 



Fig. 1. Front and rear views of the panel control loose coupler with rotating ball coupling adjustment. 


henry with the full coil. This gives a 
range with a 0.0008 mfd. condenser of 
169 to 477 meters and 377 to 1,066 meters. 
LONG WAVE PRIMARY: Three banks 
of No. 24 S. S. C. wire are required for 
the long wave primary. Like the other, 
start the winding 5/16-in. from the left 


lower. The full coil has an inductance 
of 6.0 millihenries, which, with a 0.0003 
mfd. antenna gives a maximum wave¬ 
length of 2,529 meters. 

LONG WAVE SECONDARY: Here 
again a 3^-in. tube 3*4-in. long is 
wound with No. 24 S. S. C. wire in three 













Fig. 2. Details and diagram for the loose coupler. Dimensions can be scaled off for the drawing 

was reduced one half. 


Limits 1 _ Job HLxin 6-2.1 May 2»fe,l9&l 

Scale'. Full S'^e De.RM3 ^ecfcJ_C__ 







































































































12 


Radio and Model Engineering 


banks. Start the winding J^-in. above 
the rotor shaft hole, and take off taps at 
the 21st, 57th and 145th turn, which is 
the end of the coil. The inductances at 
these three points are 0.09, 0.50, 2.50 mil¬ 
lihenries, and the wavelength ranges with 


the regular winding. After the coil has 
been given a coat of Valspar and the 
varnish dried, cut the extra turns in the 
middle and twist the two parts together 
close to the coil. There is your tap. Do 

it will 


not twist the wire too tightly or it will 





Fig. 3. Above coils for the short waves; below, the long wave primary and secondary. 


a 0.0008 mfd. G. A. STD condenser 179 
to 506, 421 to 1,192, and 942 to 2,665 
meters respectively. 

TAPPING THE COILS: There is a 
very easy way to take off taps on coils 
of this sort. When a tapping point is 
reached, instead of twisting or cutting 
the wire, merely bend the wire to one 
side and put one turn around the part 
already wound. End this extra turn just 
where it was begun, and carry on with 


break. A tap not yet twisted is shown 
in Fig. 3, near the top of the upper right 
hand coil. 

r PHIS loose coupler, fitted 
OfPeradon A with the long or short 
Coupler. wave coils wi U receive spark, 
modulated undamped waves, 
voice or music when connected with a 
crystal or audion detector. A G. A. STD 
variable condenser, 0.0008 mfd., is.needed 
for the secondary. 


















Single Circuit Audion Receiver 


13 


Single Circuit Audion Receiver 

This set, operated by two controls, tunes from 150 to 3,200 meters. 


T HE experimenter who is 
making up his first aud¬ 
ion detector set, and often 
the advanced student who builds a stand¬ 
by outfit, is usually perplexed by the mul¬ 
titude of designs possible. Starting with 
the circuit elements, he adds one thing 
and another until the set becomes too 
awkward or too expensive. 

Here is a little outfit, designed for a 
standardized L.P.F. cabinet, 10x5x5 ins., 
that brings in the signals as well as a 
loose coupler outfit, and is equal in effi¬ 
ciency and appearance to panfl sets run¬ 
ning up to seventy-five dollars in price. 
The simplicity of the design and circuit 
assures the success of the builder, for 
there are no tricks or catches. 


the^Panel? 1 front and rear of the set, 

with half-size drawings of 
the panel, inductance tube, rear panel 
support rods, and socket brackets in Fig. 
3. Locations for the holes can be scaled 
off readily 


G -A-LITE tubing, 3 ins. in 
me vun. diameter, is used as a 

form for the coil. Altho con- 
densite celleron is preferable, it is diffi¬ 
cult to wind it with two banks. The de¬ 
tails of the inductance and wavelength 
ranges are given below. These are based 
on the use of a G.A.STD. condenser of 


0.0008 mfd. 


| First 

Tap—0.02 millihenries, 0.1 
146 to 267 meters 

in., 7 

turns 

| Second 

Tap—0.05 millihenries, 0.21 
231 to 421 meter§ 

in., 17 

turns 

Third 

Tap—0.14 millihenries, 0.41 
386 to 705 meters 

in., 33 

turns 

J Fourth 

Tap—0.40 millihenries, 0.72 
653 to 1192 meters 

in., 61 

turns 




Fifth Tap—1.20 millihenries, 1.45 ins., 121 turns 
1132 to 2065 meters 

Sixth Tap—3.00 millihenries, 2.8 in., 235 turns 
1788 to 3264 meters 

A hint about winding the coil will save 
much trouble. When the wire is brought 
from the tube up to the top layer, it 
should be brought over the previous top 
turn and then down on top of the lower 
turn. Throwing up the turns in this way 
gives the effect noticeable in Fig. 1. 


T HE coil is mounted on 
brass pillars 11/16 in. 
long, threaded 6-32 clear 
thru. Screws are put in from the inside 
of the coil, and screws thru the panel 
into the other ends secure the pillars and 
coil. If the rear panel, of ^-in. L.P.F., 
\Y\x 2 y 2 ins., is mounted on the rods as 
shown, the panel will fit the 10x5x5 in. 
STD cabinet. Having the binding posts 
on the rear is a great advantage because 
it takes all the wires from the front. The 
tube socket is mounted with the positive 
filament and plate contacts toward the 
panel, and the terminals of the rheostat 
on the right, looking at the rear. The 
grid leak condenser is mounted vertically 
behind the connection panel, supported 
bv the wiring. 


A 22.5-VOLT B battery and 
6-volt storage battery 

Of til© 1 . 1 

Receiver. are needed to operate the 

tube. The antenna may be a 
single No. 14 copper wire 100 ft. long 
and 25 ft. high at each end, with a water 
pipe ground connection. However, such 
combinations as a gas pipe and water 
pipe can be substituted for the antenna 
and ground, or a wire soldered to a tin 
roof for the antenna. With the new 
Radiotron 200 tubes practically no resist¬ 
ance is needed when 6 volts are applied 
to the tube 








14 


Radio and Model Engineering 

























15 


Single Circuit Audion Receiver 








































































































16 


Radio and Model Engineering 


A Real Receiving Equipment 

This set probably introduces a new era in experimental instruments; it is a regenera¬ 
tion tuner of astonishing sensitivity for 150 to 2,600 meters. 


X> EGENERATIVE receiv- 

Tuning ers, aS man ^ an ex P ei 'i" 

Cicuit. menter knows, are not only 

difficult to handle but are 
quite expensive. Some of the variometer 
type sets have as many as nine control 
knobs, the minimum being five, exclusive 
of the audion circuits. 

The time required to tune such sets 
multiplies rapidly with the number of 
controls, because of the extremely sharp 
tuning and the frequency variations due 
to the hands, with the result that 
short calls are often lost before they can 
be tuned in. Moreover, the wavelength 
range at best is 150 to 300 meters unless 
an air or mica condenser is added in the 
secondary. 

When properly constructed, this set 
brings in signals louder than the very best 
variometer set, regenerates splendidly on 
the first half of the feed-back coil scale, 
and oscillates freely on the second half. In 
addition, it is excellent for receiving 
long waves to which a variometer outfit 
will not respond. 

Both in operating qualities and cost it 
is a logical successor to the older re¬ 
ceivers, which have so long held the in¬ 
terest of experimenters. 


A NOTHER new feataure is 
Type of introduced in this aricle, 

Construction, namely, the panel supporting 
methods. At the G. A. Com¬ 
pany we have actually built dozens of 
boxes and tried out many and varied 
schemes for supporting instrument panels, 
for the purpose of finding an inexpen¬ 
sive and at the same time good-look¬ 
ing method. The angle brass supports, 
shown in Fig. 1 , is the outcome. These are 
easily made, furnish excellent bracing for 
the panel, permit instruments to be at¬ 
tached on top or at the sides, and carry 
the rear connection panel conveniently. All 
around, it is the best system for the man 
who does not want to put four or five 
dollars into a cabinet for each instrument. 


"C'lG. 2 gives the layout of 
axid ClS tf le f ront and rear panels 

Supports. and of the angle brass sup¬ 
ports. These can be cut 
and drilled from regular stock. They 
are also sold completely made up, in 
which case the brass is nickeled. Since 
all dimensions are one-half size, they 
can be readily scaled off from the draw¬ 
ings. If a sharply pointed scriber is 
used, light lines can be made on the 
front of the panel and later sanded off, 
when the holes have been drilled, with 
No. 0 sandpaper and oil. Do not rub 
dry sandpaper on L.P.F., for it quickly 
fills up. Plenty of oil, however, keeps 
the particles floating, and they do not 
coat over the sandpaper. 


A S soon as the front panel 
has been drilled, the three 
coil mounting pillars, the 
switch, and switch points 
should be put on. An extra switch point 
is allowed at each end of the row. The 
condenser may be mounted also, but 
none of the other parts, for they will 
be in the way. 


First 

Assembly 

Job. 


T3 ANKED windings, hold a 
Winding -D terror for many experi- 
Coil. menters who have had ex¬ 

perience with them, in almost 
every case because they did not go 
about it in the right way. A simple wind¬ 
ing rig is needed, consisting of two 
round pieces to fit in the tubing, fastened 
to a %-in. shaft fitted with a handle and 
supported on two sturdy uprights. It 
is difficult to tell an Experimenter' how 
to wind the coil; he must learn by prac¬ 
tice. For a three-bank coil, the process, 
briefly, is this: 

Wind three complete turns around the 
tube, keeping the wire just as tight as 
possible. At the end of the third turn, 
bring the wire up between the second 
and third turns and wind once around. 
Then another turn between the first and 
second. At the end of the fifth turn, 







A Real Receiving Equipment 


17 


jump up between the fourth and fifth 
and wind one turn. The result should 
he a pyramid of three layers of three 
turns, then two, then one. 

When the sixth turn has been com¬ 
pleted, bring the wire down onto the 


take off the taps. This method keeps 
the winding tight and the taps out of 
the way. 

A G-A-Lite tube, 2> x / 2 ins. in diameter 
and AV 2 ins. long, carries the winding of 
No. 24 S.S.C. wire in three banks. Taps 



Fig. 1. The 150 to 2,600 meter regenerative set with a detetor and two-step amplifier. 
The latter will be described in the August issue. 


tube and put on the seventh turn, the 
eighth turn on the seventh, and the 
ninth turn on the eighth. Jump to the 
tube again, and repeat the process., lo 
take off taps, when the tapping point is 
reached, bend the wire sharply to one 
side and wind a single turn around the 
part of the coil already wound. Bring 
the end of that turn back to where it 
was started and continue with the wind¬ 
ing. After the coil has been completed 
and varnished, cut the tapping turns and 


for this 150-to 2600-meter coil are taken 
off, as shown in Fig. 2. Remember that 
a Vs -in. space is allowed after the fifth 
tap. The inductances and wavelength 
ranges with a 0.0008 mfd. series conden¬ 
ser and a 0.0003 mfd. antenna are: 

Tap 1—0.09 millihenry 

150 to 253 meters. 

Tap 2—0.16 millihenry • 

200 to 337 meters. 

Tap 3—0.30 millihenry 

270 to 462 meters. 
















18 


Radio and Model Engineering 


































































A Real Receiving Equipment 


19 



Fig. 3. End view, showing the tickler details and the connection panel. 


Tap 4—0.60 millihenry 

383 to 653 meters. 
Tap 5—1.20 millihenries 

546 to 923 meters. 
Tap 6—2.50 millihenries 

789 to 1,333 meters. 


Tap 7—5.00 millihenries 

1,066 to 1,885 meters. 
Tap 8—10.00 millihenries 

1,577 to 2665 meters. 



Fig. 4. Looking down on the condenser and inductance. 






























20 


Radio and Model Engineering 


»T»HE G-A-STD coupling 
£ he ball is made of mahog- 

BaU? mg any, turned out with a heavy 
center web. The material 
and construction make the ball free 
from the usual warping and shrink¬ 
ing experienced with thin-walled balls of 
other wood. Moreover, greater friction 
and support is given to the shaft, so it 
will not run out of true or become loose. 

To obtain sufficient inductance to 
make the set oscillate over such a wide 
wavelength range, the ball is wound on 
each side with two layers of No. 24 
S.S.C. wire. The winding is started at 
the outside, running up to the top, then, 
jumping down to the outside, the wind¬ 
ing is run up again. This is repeated on 
the other side, winding in the opposite 
direction so that the two halves will 
actually be in the same direction. The 
adjacent ends of the two halves are sol¬ 
dered together and the outside ends run 
to the two parts of the split shaft. 


HTH REE GA-STD coil 
Mounting J. mounting pillars are re¬ 
coils. quired, one at the right and 

two at the left, as shown 
in Fig. 2. Holes in the tube for 
the tickler shaft must be located care¬ 
fully or the tickler dial will not turn 
true. The shafting is of *4-in. brass rod. 
Since the tickler ball is already drilled 
with a small guiding hole, it is only nec¬ 
essary to enlarge it with a 34-in. drill. 

Before the tickler is put in place, two 
small pieces, 24 by 134 ins., should be 
cut from No. 24 spring brass sheet, and 
drilled with a 34“i n - hole in their cen¬ 
ters. They are for spacers between the 
ball and the inside of the inductance 
tube. When the coil has been mounted, 
the shaft, carrying the dial, is put in 
from the panel, a spacer fitted over it, 
and the shaft pushed into the ball. This 
is repeated from the rear. The wires 
from the tickler are then soldered to the 
ends of the shaft, Fig. 3, and pigtails 
soldered on outside as in Fig. 4. Finally 
a 1-in. screw is put through the tube, 
Fig. 3, 3/16 in. from the end, to act as 
a stop for the tickler. This also serves 
as a terminal for the start of the wind¬ 
ing, as may be seen in Fig. 4. 


Vf/HTH the taps, covered 
Con nect mg TT with Empire tubing, sol- 
Finishing. dered to the points and the 
condenser in place, the next 
step is to assemble the panel supports and 
the connection panel. 

Round head 4-36 machine screws hold 
the angle brass strips together. Holes 


in the angle brass can be drilled more 
readily if a jig is made of 3/8 by l/16th 
in. brass strip, bent over at one end. 
The holes are first laid out on this strip. 
Then, by hooking it on one end of the 
angle brass, the holes can be located 
quickly and exactly. 

The binding posts should be put in 
place, with No.. 6 soldering lugs, and 
tightened before the panel is fitted to 
the panel supports. Fig. 5 gives the 
connections, and they can be traced out 
in Fig. 4. 

/"'|NLY an audion detector 
Operating V/ an d accessories are re¬ 
set. quired in addition to the re¬ 

ceiver. A variable grid leak 
or grid condenser is not necessary; 
they should be fixed, of approximately 1 
megohm and 0.0005 mfd. respectively. 



Fig 5. Wiring diogram of the complete outfit. 


If, at maximum tickler coupling, the 
set does not oscillate, as indicated by a 
plucking sound when the grid post is 
touched, the connections to the tickler 
should be reversed. Sometimes it is nec¬ 
essary to put a 0.001 mfd. phone con¬ 
denser around the B battery and tele¬ 
phones. This is required when an .am¬ 
plifier is used. A little experimenting 
will show whether one, two or three are 
needed around the primary of the trans¬ 
former. 

To tune the set, the tickler is slightly 
advanced, and the switch and variable 
condenser adjusted until signals come 
in. Increasing the tickler brings up the 
signals to the point of oscillation, when 
they become mushy. 

With the regeneration obtained sig¬ 
nals come in loudly which, without the 
tickler, cannot be heard at all. It will 
be found that the more closely the set 
is tuned, the greater is the regenerative 
action. 



































A Real Receiving Equipment 


21 


A Real Receiving Equipment 

Altho this detector and two-step amplifier is designed particularly for the 
150- to 2,600-meter regenerative set , it will work admirably with any receiver 


r T'HERE are so many differ- 
Note ^.® n ent types of amplifiers on 

Design. er the market that one may 

gain the impression that any 
combination of sockets, rheostats, and 
transformers will give good results. Ex¬ 
perimenters who have neither time nor 


sistance across the grid and filament of 
each tube. Leakage, either thru or over 
the surface of the material of which 
the base is composed, slight as it 
may be, reduces the tiny voltage applied 
to the grid by the incoming signal. The 
result of this loss, possibly not percepti- 



Fig. 2 . A machine shop is not needed to turn out business-like radio 
apparatus if a correct design is chosen. 


equipment to make comparative tests are 
particularly given to drawing conclusions 
not based on laboratory results but mere 
impressions, when, as a matter of fact, 
two stations with identical apparatus may 
show quite different operating characteris¬ 
tics. 

T HE sockets to be used 
may be taken up first. 
Details. Experimenters cannot be im¬ 

pressed too forcibly with the 
necessity of maintaining a maximum re- 


ble in the detector, is surprising when 
multiplied in successive stages of ampli¬ 
fication. 

It is for this reason that L.P.F. was 
chosen for the bases of the new GA-STD- 
A1 tube sockets. A very striking example 
of low resistances in the so-called perfect 
molded compositions is that of a grid 
leak mounting widely sold by one of the 
leading manufacturers. The leak is fitted 
between springs set in a molded base. 
Altho the only conductivity was supposed 












22 


Radio and Model Engineering 



to occur in the 1,000,000-ohm grid leak, a 
number of the moutings showed as low as 
50,000 ohms across the terminals, render¬ 
ing the grid leak worthless as a high re¬ 
sistance by-pass. 

Another important feature is the tight¬ 
ness of the audion in the socket tube,. If 


TF the amplifier is to pro- 
Seiection M. ( j uce max imum signals the 

Transformers transformers must be of a 
design to conform with cer¬ 
tain requirements. The ordinary square 
core transformer is not to be recom¬ 
mended in spite of its lower price. In the 
first place, this type is generally of too low 


■ 

_ 


Fig:. 1. A 150- to 2,600-meter receiving set which can be assembled with no other tools 
but a hand drill, screw driver, pliers, and soldering iron. 


it is loose the springs will not make, per¬ 
fect contact and even slight vibration will 
cause a varying resistance between the 
contact springs and tube pins, giving a 
noise that is often supposed to be from 
the B batteries. 


impedance to match the tubes. These 
transformers howl readily because of their 
large exterior magnetic field. 

The shell type core, such as is employed 
on the Federal transformers, permits the 
use of a very small winding yet it gives 



























A Real Receiving Equipment 


23 


r 



REAR PANEL 



Des.by —tu3©. 

THE&ENERAL APPARATUS C0.lnt. 

Dr.by I L L. 

DET.-»fc-STP.AMP. 

Ch.by 

IhCbfl.^®. 

Piece Pt. 

Panels 

Limits 

Job RandM8-il 

JAuo.ia.l98l 1 

Scale' Full Site 

Dr.RM6 

Sheet \~Z \ 

























































































24 


Radio and Model Engineering 


a high impedance. When wired properly 
these transformers can be placed close to¬ 
gether without any interference from 
howling on account of their slight ex¬ 
terior field. While the shell type is 
strongly recommended in preference to 
the square core, the advantages are only 
found in types where the core laminations 
are at right angles to the turns on the 
coil. Some transformers have circular 
laminations in the same direction as the 
turns on the winding with the result that 
the magnetic field is perfectly short cir¬ 
cuited. In addition to introducing serious 


bination giving minimum inter-tube coup- 
ling and the shortest possible connections, 
both important features. In the first 1 
model the jacks were placed beneath the j 
rheostats. This was altered, as can be 
seen in Fig. 1, for the telephone cord 
hung down over the receiving set. In J 
any set it is better to keep the jacks at 1 
one side. 

A special convenience is the angle brass 
supports for the panel. They make it 
possible to mount the detector and am- j 
plifier above the receiving set, or support 



Fig. 5. Looking down on the amplifier, showing the effect of symetrical arrangement. 


it directly on the table. The arrangement 
of the binding posts is such that only 
four connecting wires to the receiver 
are required at the back. All the 
wiring which, at best, does not add to the 
appearance of the outfit is out of sight, 
giving the front a clean cut appearance. 

Figs. 2 and 3 show the layout of the 
parts. The holes are symetrically lined 
up to make the location of their centers 
easy, and a minimum number of drill sizes 
employed. Since the original drawing in 
Fig. 3 has been reduced exactly one-half 
the dimensions can be quickly scaled off 
with dividers and transferred to the panels 
with a square and scriber. The angle 
brass supports are identical to those used 
for the receiving set, dimensions for which 
have been given already. 


losses it causes distortion in the reception 
of speech and music. Other spe.cial de¬ 
signs product resonance effects for given 
audio frequencies. That is all right for 
spark reception, but bad for telephonic 
signals. 

A LL that is gained by care¬ 
ful selection of parts can 
Features. t> e nullified by in correct me¬ 
chanical design. In the set 
shown in Fig. 1 a combination of efficient 
arrangement and convenience was at¬ 
tempted which proved quite successful in 
the completed instrument. 

The arrangement of the parts is a modi¬ 
fication of the GA-STD-A5 and -A6 de¬ 
tector and amplifiers, resulting in a com- 



















A Real Receiving Equipment 


25 


A LL the panels and the 
supports should be drilled 
Instrument. and sanded or polished be¬ 
fore the assembly is started. 
Put the transformers and sockets on the 
bottom panel first, making sure that they 
are set in the proper direction. Then come 
the rheostats and jacks on the, front panel. 
The binding posts should be tightened 
firmly on the back panel because they 
are difficult to get at once the panels are 
assembled on the supports. 

The, greatest care must be exercised in 
wiring. Tinned square copper wire, com¬ 
ing in straightened lengths, makes this 


& 

<t> 


heavy current drawn by three tubes the 
plate,s of the battery, if of a cheap make, 
are very liable to buckle, and for this rea¬ 
son a standard make, such as the Wither- 
bee, is recommended. Two 22^-volt B 
batteries are also needed. When wired 
as indicated by the connection panel 
marking, 22^ volts are applied to the de¬ 
tector and 45 to the amplifiers. 

The only connections to the, receiving 
set are for the grid and filament and the 
tickler coil. If the amplifier is used with 
a variometer type receiver the plate vario¬ 
meter should be joined to the posts 
marked P P. In the case of an ordinary 




Des.by — 

THE &EHERAL APPARATU5 GO..Inc. 

Dr. by I LL. 

DET>"» Z-STP. AMR 

Ch.by— 

InChq 

Piece Pt. 

Wirinij Diagram 

Limits 

Job RandM8-2l 

Au.<,.IZ,l92l 

Scald Full Size 

Dr. RM7 

Sheet Z~Z 


work much easier. What additional time 
is spent in fitting the wires is well repaid 
in the results and appearance. The, great¬ 
est danger lies in excessive use of sol¬ 
dering paste. No tinning is needed on 
the wires if they are wiped off with a clean 
cloth, and the soldering lugs can be tinned 
before the parts are mounted. Then, in 
connecting up, no paste at all, or the tin¬ 
iest bit, is needed. 

T HE first requisite for the 
ine successful operation o f 

instrument, an amplifier is a good fila¬ 
ment lighting battery. Tubes 
now available take almost the full 6 volts 
of the battery, and will not operate when 
this voltage drops ,appreciably. With the 


non-oscillating set the P P posts should 
be short circuited to close the plate cir¬ 
cuit. 

Frequently a regenerative receiver will 
not oscillate,, when connected with an am¬ 
plifier, unless a fixed condenser of 0.001 
or 0.002 mfd. is put across the primary of 
the first amplifying transformer. This is 
not shown in the wiring diagram because 
it is not always needed. 

The completed instrument shown in the 
accompanying illustrations, tested against 
two other standard makes, gave apprecia¬ 
bly louder signals, due to the careful at¬ 
tention given to each detail of this outfit. 
Those results can be readily duplicated by 
any experimenter who is equally conscien¬ 
tious about his work. 


















































































26 


Radio and Model Engineering 


Simple Crystal Receiver for Phone Reception 

The first receiving set „ The beginner should start out with a receiver so simple 
that he will have no difficulty in making it worn . 


The 

First 

Problem 


a man makes up 
his mind to install a 


radio set he generally asks a 
friend who has a station al¬ 
ready for advice as to what he should buy. 
He is usually told to get an audion de¬ 
tector outfit, with a loose coupler, conden¬ 
sers, and so many other things, that if he 
does not lose heart immediately, he prob¬ 
ably will before he learns to use the ap¬ 
paratus. 

The proper start is with a set so simple 
that it cannot fail to work, yet designed to 


signals very loudly, but with broader tun¬ 
ing than is obtained on a loosely coupled 
set. 

On the front of the panel are the switch 
controlling the inductance and a crystal 
detector; at the rear the tuning coil and 
phone condenser. The switch is used in 
preference to a slider because the latter 
wears away the, wire, leaving a copper 
dust to short circuit the winding. Ga¬ 
lena is the most sensitive crystal for the 
detector, and, with a fine copper wire for 
the contact, will keep its adjustment. 



Fig. 1. Front and rear views of the beginner’s receiver. Note the simplicity 
of the wiring and assembly. 


conform with standard practice. In addi¬ 
tion, the arrangement should be such that 
other instruments can be added to im¬ 
prove the operation as the beginner’s ex¬ 
perience is broadened. To get the most 
fun from the set it must be strictly home 
made. 


A. 

Beginner’s 

Outfit. 


\ receiving set which con- 
forms with the require¬ 
ments just given is shown in 
Fig. 1. Built on a standard 
5- by 5-in. panel, all the parts are con¬ 
veniently located and so connected that 
there is no mystery about the circuit. 
This outfit is commonly known as a sin¬ 
gle-circuit receiver, a type that brings in 


TTIG. 2 shows the holes in 
fC'parts V the 5- by 5- by 3/16-in. 

Together. L.P.F. panel. This material 

can be drilled readily w T ith an 

ordinary hand drill after the holes have 
been located with a center punch. A 
drawing is also given for the panel sup¬ 
port brackets, cut from by 1/16-in. 
brass strip. 


The hardest work is on the coil. This 
is wound with No. 24 S.S.C. wire on a 
G. A.-Lite tube 3 ins. in diameter. To 
start the winding, put a pin into the tube 
y 2 in. from one end, and twist the wire 
around it. Then wind to the, first tap as 









Simple Cryst al Receiver for Phone Reception 


indicated in Fig. 2. At this point bend 
the wire toward the start of the coil and 
put one turn around the part already 
wound. Bring the end of this turn 
around to the place where it was started 
and wind on to the ne,xt tap. Secure the 
last turn with another pin. When the 
coil is finished, cut those extra turns, 
twist them together where they started, 
and bring them out for taps to the switch. 

Before the coil is mounted, the detec¬ 
tor parts, switch, switch points, fixed 
condenser, and binding posts should be 
put on. Then comes the coil, supported 
on the two mounting pillars. Great care, 
must be taken in connecting the taps to 
the switch point, so that extra soldering 


only way to insure perfect and permanent 
contact, and is well worth the additional 
work involved. 


Operating T HIS reCei ' fer is deigned 

the to operate on a single- 

Receiver wire antenna 100 to 150 ft. 

long and 30 to 50 ft. high, 
with the lead-in brought from any part 
of the antenna. One 3-in. HF insulator 
is needed at each e,nd. The lead-in should 
be connected to the upper binding post 
on the panel, and a wire from a water 
pipe to the lower. The phones, preferably 
2,000-ohm Murdocks, go to the center 
posts. A buzzer is needed to test the ad¬ 
justment of the detector. It should be 
connected with a dry cell and push button, 



riff. 2. Exactly one-half size. Showing the parts and the wiring of the completed outfit. 


paste will not run over the panel. _ An old 
tooth brush is handy for cleaning out 
of the way places. The best practice is 
to increase controls by turning clock¬ 
wise. Therefor the, first tap should be 
brought to the left hand switch point, and 
so on until the last tap goes to the last 
right hand point. 

Connections are given in Fig. 2. Made 
with square tinned copper wire, they can 
be easily fitted and soldered. That is the 


with a wire running from one terminal of 
the buzze,r to the ground lead. When 
the detector is in adjustment the buzzing 
can be heard in the telephone. To tune 
the set for incoming signals simply turn 
the switch back and forth until sounds 
are heard at maximum strength. 

If this outfit is properly installed, it 
will tune from 200 to 1,000 meters and 
bring in the larger stations up to 500 
miles away. 




























































28 


Radio and Model Engineering 


Radio Frequency Amplification at 200 Meters 

This set, designed for reception on ijo to 250 meters, combines radio frequency 
amplification and regeneration in a receiver critically sharp in tuning and as easy 

to build as it is inexpensive 


In fact, many experimenters have been 
more successful with the familiar loosely 
coupled receiver and tickler coil, and they 
claim that no losses are apparent from 
the use of a small variable condenser 


T HE urge for something 
new, which all radio men 
experience at frequent inter¬ 
vals, is probably responsible 
for the insurgent tendency to get away 



>«| 

1H tiliih&iil 


■ll!* 


Fig:. 1. A radio frequency amplifier and detector with tuning circuits for 150 to 350 meters. 
Addition audio frequency amplification can be used if desired. 


from the old standby—the variometer re¬ 
ceiver. The latter is being warmly de¬ 
fended from many quarters, and its strong 
points cannot be denied. However, it is 
not fair to experimenters for those who 
are personally interested in the continued 
use of the variometer sets to attempt the 
discouragement of development work 
along other lines, for it is entirely possible 
that something better can be worked out. 


across the secondary circuit. Any vari¬ 
ometer set that tunes over a range of • 
more than 150 to 350 meters has mica 
condensers in the secondary. 

At the G. A. we have tried out many 
different circuits, with varying results. 
Different characteristics often make a cir¬ 
cuit good for particular requirements but 
not broadly adaptable. One circuit, how¬ 
ever, has stood out from the rest, a circuit 









Radio Frequency Amplification at 200 Meters 


familiar to some in Army or Navy re¬ 
search sections, but not generally known 
to experimenters. It is the tuned imped¬ 
ance radio frequency amplifier. While 
this circuit is not proposed as an open 
sesame to the door of optimum methods, 
it has several unique advantages which 
other circuits do not possess. 

A NY radio frequency am- 
Fr^uenc ^ plifier increases the ampli- 
Ampiitter 9 ' tude the incoming oscilla¬ 
tions without affecting their 
character. A telephone in the output cir- 


static as much as the audio frequency 
type, as will be explained later on. 

With the methods now available, trans¬ 
former coupling or similar systems can¬ 
not be employed on wavelengths below 
600 meters. Reasons for this have been 
set forth by Armstrong in his paper on 
“A New System of Short Wave Amplifi- 

HPUNED impedance coup- 
ling, fortunately, offers a 
simple alternative method for 
one step. Two steps can be 


Tuned 

Impedance 

Coupling 



Fig. 2. Side and rear views of the receiver. 


cuit of a radio frequency amplifier pro¬ 
duces no sound, as the oscillations of the 
input circuit are not rectified until they 
are put thru a detector. If the incoming 
signals are strong enough to operate a 
detector, an audio frequency amplifier 
will amplify them, but a radio frequency 
amplifier produces the same effect as 
moving the receiving station nearer the 
transmitter because it amplifies any im¬ 
pulses without regard to their weakness. 
In fact, signals can be received when 
three or more stages of radio frequency 
amplification are required to bring them 
up to a strength sufficient to act upon a 
detector. 

Another advantage of this type of am¬ 
plification is that it does not amplify 


employed, but the tuning with more steps 
becomes so extremely sharp as to con¬ 
stitute a disadvantage. Fig. 3 shows a 
simplified diagram of impedance coupled 
radio frequency amplifier. In the plate 
circuit of the first tube are a coil and 
condenser of such dimensions that they 
can be tuned to the frequency of the in¬ 
coming waves. The direct current from 
the plate battery has a low resistance 
path thru the coil, but the tuned parallel 
circuit presents an infinite impedance, 
theoretically, to the incoming radio fre¬ 
quency, serving the same purpose as a 
resistance in a resistance coupled ampli- 


lProceedings of The Institute of Radio Engi¬ 
neers, February, 1921. Sold by The General Ap¬ 
paratus Co., Inc., 570 W. 184th St., New York 
City. $1.50 per copy. 
















30 


Radio and Model Engineering 


fier. The second tube, with its grid con¬ 
denser, acts as a detector, to which audio 
frequency amplifiers can be added if de¬ 
sired. Since there is no tuning to static 
disturbances, they tend to pass d : rectly 
thru the impedance coil, producng only 
a slight effect upon the detector. 

T HE receiver shown in the 
accompanying illustrations 
is a strictly 200-meter set, as 
the wavelength range, with an 
antenna of 0.0003 mfd., is only 150 to 


General 
Description 
of Set 


pendance condenser. The radio frequency 
amplifier tube, on the left, and the de¬ 
tector, on the right, are adjusted by their 
respective rheostats below. Binding posts 
are carried on the rear connection panel 
mounted on an angle brass frame. 

An idea of the simplicity of the circuit 
may be gained from the fact that there 
are only 14 separate wires used to join 
the instruments. If an audio frequency 
amplifier is employed, it can be wired, to 
posts provided at the rear. Fig 3 shows 



Des.b.y ~fa<<58. 

THE &EMERAL APPARATUS CO.Ine. 

Dr by I.L.L. 

RECEIVER*"WPLIFIER 

Gb.by 

ln.Cb.Q-&r©» 

Piece Pt. 

Panel 

Limits: 

dob RanJM9-&l 

Sept. IT. 192,1 

Scale! Foil She 

p>-^a_ 

Sheet 1-3 


Fig. 4. One-half size. Seale drawing of the instrument panel. 


350 meters. Tuning in the antenna cir¬ 
cuit is accomplished by a fixed inductance 
mounted at the rear of the panel and a 
0.0008 mfd. condenser at the lower left 
hand corner of the panel. The impend- 
ance inductance, also of a fixed value, is 
adjustably coupled to the antenna coil, its 
position being controlled by the center 
dial. On the right is a 0:0008 mfd. im- 


the diagram. 


The 

Parts 

Required 


'J'HIS receiver is made up 
of a front instrument 
panel, 10 by l]/ 2 by 3-16 in. 
rear connection panel iy 2 by 
2/ 2 by l /g in., cut from a standard sheet 
10 by 2 l / 2 ins., angle brass frames, two 
0.0008 mfd. condensers, two rheostats and 


















Radio Frequency Amplification at 200 Meters 


I sockets, fixed inductance, tickler, and grid 
1 condenser. No switches are required. 




Fig. 4 shows at one-half scale the lay- 
1 out of the panel. To take off the dimen- 
I sions it is only necessary to measure on 
I the drawing and double the distances, 
j Drill sizes are indicated; two circles call 
for countersinking. Thru standardization 
<i of the parts, a minimum variety of drill 
sizes are needed. 


A G-A-Lite tube, 3^ ins. in diameter 


31 


furnished with ^-in. holes which give a 
tight fit on a %-in. rod. 

The only other difficult work is in mak¬ 
ing the brackets for the sockets. They 
are cut from by 1-16-in. strip, drilled 
and bent as in Fig. 3. To obtain a per¬ 
fect adjustment of the sockets it may be 
necessary to file the rear holes of the 
lower brackets into the shape of slots. 
The sockets are furnished with short 
posts for mounting, threaded 8-32 and 
held by %-\n. screws. These screws 
should be removed and 1-in. 8-32 screws 



Fig. 3. One-half scale. Circuit details and scale drawings of the support frames. 


by 3 ins. long, wound with 28 turns 
of No. 20 D.C.C. wire, is held by two 
supporting pillars at the right of the 
shaft- The screw heads are hidden by 
the tickler dial. A standard 3-in. tickler 
ball is mounted in the coil by a two sec¬ 
tion shaft. It has been found quite satis¬ 
factory to use holes drilled in the G-A- 
Lite tubing for shaft bearings. The tickler 
ball is wound with one layer of No. 20 
D.C.C. wire, with the start of the coil 
soldered to one-half o£ the brass 

shaft, and the end to the other half. 
Rig-tail leads may be. soldered to the shaft 
or friction bearings of spring, brass fas¬ 
tened to the tube and pressing on the 
shaft are satisfactory. These balls- are 


put in their places to extend thru the 
brackets. 

Eight binding posts are mounted on the 
rear panel. The two rows are 1 in. apart 
and the posts separated by V/z ins. 

W HEN the parts are ready 
for assembling, the rheo- 
Stats should be put on first, 
then the coil and tickler, after 
all leads have been soldered, next the con¬ 
densers, and finally the angle brass frames 
without the rear panel. Because the rear 
panel is in the way during part of the 
soldering, all wires not running to bind¬ 
ing posts shoul» be fitted first. Instead 























































































32 


Radio a$d Model Engineering 


of running a wire from the ground side 
of the left hand condenser to the ground 
post, both these terminals are connected 
to the left frame. Other details of con¬ 
nections are given in Fig. 3. 

Hr HIS receiver has a num- 
Skiggestions X b er Q £ p ecu li ar ities which 
operating must be observed by actual 
operation, and the tuning is so 
sharp that the best results can be obtained 
only by the correct handling of the con¬ 
trols. 

For best understanding, the left hand 
condenser may be considered as the pri¬ 


mary control and the right hand con¬ 
denser and tickler the secondary. This J 
is because the tickler gives a wavelength 
control effect which makes it necessary 
to adjust the tickler and impendance cir¬ 
cuit condenser simultaneously. It will be 
noted that a 180° dial is used on the j 
tickler as it is sometimes put on one side 
or the other of zero coupling. 

Spark, telephone, or undamped tele¬ 
graph stations can be heard with this re¬ 
ceiver clearly and without distortion. At 
the same time the receiving range is in¬ 
creased beyond that which can be covered 
with any number of audio frequency am¬ 
plifiers. 


Notes on Amplifying Transformers and Plate Batteries 


Several types of amplifying transform¬ 
ers, including the new GA-STD-A14, 
have the terminals marked Pi, P2 and Si, 
S2. This does not really indicate, however, 
the way in which the transformer should 
be connected. The numerals following 
the initial mean that the terminal marked 
1 is connected with the beginning of the 
winding and 2 to the end of the winding. 
The inside or start of the primary wind¬ 
ing should go to the plate and the start 
of the secondary winding to the grid. 
Then the P2 terminal will be connected 
to the filament side of the circuit as well 
as S2. If the transformer is not con¬ 
nected in this way it will not operate to 
the maximum efficiency. Other trans¬ 
formers, such as the Western Electric 
have their terminals marked, 1, 2, 3, 4. 
Then 1 indicates the start. of the pri¬ 
mary, 2 the end of the primary, 3 the 
start of the secondary, and 4 the out¬ 
side. The same rule applies to these trans¬ 
formers as to the others in regard to 
the connections to the terminals. 

Several unusual features are incorpor¬ 
ated in the GA-STD-A14 transformer. 
In the first place it is absolutely water 
tight. This eliminates the corosion 
caused by the effect of moisture upon 
the extremely fine wire with which trans¬ 
formers are wound. The coil itself is 
not made with a string winding which 
increases the size of the coil and takes 
the winding farther away from the core 
but is wound with a sheet of insulating 
material between each individual layer. 

A very novel feature is the design of 
the transformer itself, details of which 
have not yet been made public although 
they can be discovered bv breaking, the 
transformer. The effect of perfect shield¬ 
ing is accomplished without the use of 
anv iron laminations. As a result, dis¬ 
tortion and the familiar transformer 


noises frequently attributed to the tube 
eliminated. These effects are frequently 
very marked when three steps of amplifi¬ 
cation are employed on transformers 
where corrective measures have not been 
taken. Experimenters are not advised to 
employ more than three steps of audio 
frequency amplification using the-Al4 
transformers because the power amplifi¬ 
cation is so great that the windings are, 
liable to be burned out- After the third 
step a stepdown transformer and power 
tube such as a radiotron UV202 should 
be used with 135 to 300 volts on the 
plate. 

Aside from the increase in operating 
life obtained by the new design of the 
GA-STD-All and -Al2 plate batteries 
they have a particular appeal to those 
purchasing batteries by mail because of 
their greatly reduced weight over the size 
formerly required for equally operating 
life, and to those who are using portable 
receiving or vacuum tube transmitting ap-i 
paratus. It is possible, for example, to 
use three of the -Al2 batteries to ( get 
135 volts with a weight of only 12*'lbs. 
There is nothing that can be used to 
give this voltage that will compare at all 
in lightness with this source of plate 
supply. Very simply portable transmit¬ 
ting equipment has been made up using 
two UV-202 bulbs on three -Al2 bat¬ 
teries and distances as high as 40 miles 
have been covered. 

The larger type has a center tap to 
give 22 1-2 volts for detectors and 45 
volts for amplifiers. No variation of 
plate voltage is found necessary in ordin¬ 
ary practice although a filament battery 
potentiometer can be employed if this is 
required. The absence of taps also does 
away with accidental short circuiting 
which may, if left over night, ruin the 
batterv. 









12,000 to 20,000 Meter Receiver 


33 


12,000 to 20,000 Meter Receiver 

Long Wave Reception Is Coming Bach, Not Only Because It Is Interesting and 
Good Code Practice, But Because It Affords Opportunity 
For Much Experimental Work. 


TlACK in the days when 
onLm.g°£ve four-foot inductances 

Reception gave a spectacular appear¬ 

ance to a receiving station 
and the controls were operated by yard¬ 
sticks, long wave reception from foreign 
stations was quite popular, but it was 
dropped later as a temporary fad. Now, 
however, interest of a more permanent and 
serious character is reviving for several 
reasons. Long wave signals are the easiest 
to receive over great distances, so that the 
man with an indoor antenna or a small 
loop can get them. Stations are always 
transmitting, and at slow speed, giving bet¬ 
ter code practice than a practice machine 
whose records are soon learned. 

For testing work long waves give a 
steady source of signals, comparatively free 
from erratic results obtained on short 
waves. Several stations can be heard at 
any time during the twenty-four hours. 

T HREE views of a receiver 
for this purpose are given, 
Circuits showing the simplicity of the 

instrument and the wiring. To 
cut down the work and expense of the 
coils, a single circuit is employed, using a 
stationary coil of fixed inductance and a 
0.0008 mfd. condenser in shunt in the an¬ 
tenna circuit, with a movable coil in the 
plate circuit. With an intenna of 0.0003 
mfd. this receiver will tune from 12,000 to 
20,000 m. In the first tests on the circuit, 
the conventional cross-wound concentrated 
coils were used, but, surprising as it may 
seem, signals were increased 50 to 75% 
when the layer-wound coils were substi¬ 
tuted. One reason is that the D. C. resist¬ 
ance is much lower, and losses due to var¬ 
nish are less because varnish is only applied 
to the outside layer. . 

The smooth and easy operation of the 
set and the fact that it picks up European 
stations on a single detector tube make/ it 
a real pleasure to operate. 


Panel 

and 

Supports 


F IG. 4 gives the details of 
the 7^xl0x3/16-in. panel 
at one-half scale. The only 
hard part is the slot which is 
made by drilling a row of holes and filling. 
No dimensions for the angle brass supports 
are given, as it is of the conventional type 


formerly described, measuring 7 z / 2 by 6 ins. 
A regular 10- by 2 x / 2 - by ^-in. panel, 
carrying six binding posts, is secured at 
the rear. At each end are $4- by 1/16-in. 
strips carrying the tickler coil support rods. 
These should not be soldered to the frames, 
however, until the coils are completed. 

T N Fig. 3 the coils are illus- 
the min8: trated as they appear when 

Coils ready to mount. A 3*4-in. 

G-A-Lite tube, 6 ins. long, is 
used for the antenna coil. The winding is 
started in. from one end. First, 44 turns 
are wound on then the wire is brought up 
between the 43rd and 44th turns, and 43 
turns are wound back over the first layer. 
This is continued, winding back and forth 
until 11 layers have been put on, giving 44, 
43, 42, 41, 40, 39, 38, 37, 36, 35, 34 turns per 
layer, or a total of 429 turns per section. 
At the end of the section the process is 
repeated until, with three sections, an in¬ 
ductance of 124.00 millihenries is obtained. 
The end of the winding is brought to a 
screw and lug 14 in. from the end of the 
tube. 

A G-A-Lite tube 3 ins. long and 4j4 ins. 
in diameter is required for the tickler. The 
winding is started in. in, and made up 
in two sections of 7 layers, having 44, 43, 
42, 41, 40, 39, 38 turns per layer. A light 
coat of Valspar varnish, baked in a gentle 
heat, will hold the wire permanently. Next 
come the angle pieces which slide on the 
3/16-in. rods and the 3/16-in. rod by which 
the coil is moved, both of which are shown 
in Fig. 4. Flat head screws are used in all 
cases, with the heads inside the tube to 
give clearance over the antenna inductance. 

It is necessary to set the antenna coil 
back from the panel quite a distance. 
Therefore, in addition to the regular GA- 
STD-14 coil mounting pillars, held to the 
tube by j4-in. 6-32 F.H. screws, two GA- 
STD-8 threaded posts are put over 1-in. 
6-32 F.H. screws from the front of the 
panel, and the screws threaded into the coil 
mounting pillars. 

U ITH the parts ready, the 
Assembhng ▼▼ SU pp or ting frames should 
Wiring’ be put on the panel, and the 

coils mounted, without cutting 
off the 3/16-in. rods to length. Then 










34 


Radio and Model Engineering 



Fig - . 1. Two controls only are used to tune from 12,000 to 26,000 meters, covering the range of 

trans-Atlantic stations. 
























Fig 2. Bottom anrl rear views of the long wave receiver, as fine a set as you ever operated. 

Suitable for general reception or experimenting. 


12,000 to 20,000 Meter Receiver 


35 




























36 


Radio and Model Engineering 


comes the condenser, back panel with the 
binding posts already on, and the wiring. 
Two flexible leads of phosphor bronze strip 
are used between the tickler terminals and 
the corresponding binding posts. A dia¬ 
gram is given in Fig. 4. 

Hints T 10 wire up the receiver it is 

on" S A on ly necessary to attach 

Operating: the antenna and ground, run 

wires from the G and F posts 
to corresponding terminals on the detector, 
and to insert the tickler in the plate circuit. 
Reverse the tickler connections if the cir- 


The terminals of the loop should be con¬ 
nected to the antenna and ground con¬ 
nections on the receiver. In addition a 
condenser such as the 0.0002 mfd. 
GA-STD-A15 is recommended. 

The loop should be mounted so as to be 
swung easily on its axis in whatever di¬ 
rection signals are to be received. While 
a loop of this sort is not as efficient as a 
single wire antenna 30 ft. high and 200 
to 300 ft. long, the size with which the 
set is expected to be used, long distance 
reception can be accomplished much more 
readily than on the short waves. 



Fig:. 3. Details of the completed coils, ready to mount on the panels, the tickler at the left and 

the antenna coil on the rigrlit. 


cuit does not oscillate. When an amplifier 
is added, put a 0.001 mfd. phone condenser 
across the transformer and plate battery of 
the detector; otherwise the set will not 
oscillate properly. With two or three steps 
of amplification foreign stations come in 
with extreme loudness. 

Many experimenters have had excellent 
results with indoor loop antennas work¬ 
ing on long waves. To use with this re¬ 
ceiver a frame is suggested with 40 turns 
of No. 20 D.C.C. wire spaced ^-in. apart. 


Radio dealers can use the signals from 
long wave stations advantageously for 
demonstration purposes, attaching two or 
three stages of amplification and a loud¬ 
speaker to the receiver. This is better 
than depending upon the irregular short 
wave signals because the former transmit 
steadily, oftentimes hour after hour, a 
great advantage when the signals are de¬ 
pended upon to attract the attention of 
people passing by the store. A public 
code practice can also be furnished in this 
way. 









12,000 to 20,000 Meter Receiver 


37 












































































































38 


Radio and Model Engineering 


150 to 600 Meter Regenerative Set 

The condenser-tuned secondary in this receiver has the advantage of a larger 
wavelength range than can be obtained with a grid variometer. 


T HERE are now many 
users of short wave regen¬ 
erative receivers beside the 
regular radio experimenters, for 
those who buy crystal sets for broadcast recep¬ 
tion soon recognize the short-comings of those 
outfits, and find the need of a receiver that will 
cut out interference as well as bring in signals 
with greater strength. 

For long distance or broadcast reception this 
outfit comes well recommended, for excellent 


Use of 

This 

Set 


In this receiver there is an 
antenna inductance, controlled 
by small and large step switches, 
to which is coupled a ball 
carrying the entire secondary inductance. Only 
the variable condenser is used to tune the second¬ 
ary circuit. The plate variometer gives the 
tuning necessary to make the set regenerate or 
oscillate. A detector is provided in this outfit, 
to which an amplifier can be attached by the 
binding posts on the right. When the detector 
only is in use, phones are plugged in at the jack. 


The 

Circuits 

Used 



Fig. 1. In appearance and operation, a first class receiver 


results have been obtained on 200 and 360 
meters. With two steps of amplification, when 
copying Newark at the G. A. laboratory, a pair 
of Murdock receivers were overloaded so that 
the entire casing vibrated from the movement 
of the diaphragm. Dealers and experimenters 
who make up apparatus to sell will find this set 
sure and dependable, one on which they can 
guarantee maximum results. A few simple 
instructions are required, however, before the 
set is put in the hands of a beginner because 
of the extreme sharpness of the tuning. In 
practice, the least amount that the secondary 
condenser can be moved will bring phone signals 
in or out. Of special advantage is the shielding 
obtained by using the new german silver dials. 


One of the new Federal plugs, which takes the 
phone tips, is illustrated. 

Some experimenters will exclaim over the use 
of what appears to be a large capacity in the 
secondary, as compared with the variometer 
tuned circuit. Actually, however, a very small 
capacity is employed at the 200-meter setting, 
and the distributed capacity is low. With a 
variometer there is a comparatively high 
distributed capacity, not only between the 
windings of the variometer but in the shellac 
or varnish used. No grid variometer will tune 
over a range of more than 150 to 350 meters. 
For longer wavelengths the common practice 
is to shunt the secondary circuit with mica 
















COUP 


150 to 600 Meter Regenerative Receiver 


39 




Fig. 4 


Scale drawingW the panel, reduced to one half size 

































































40 


Radio and Model Engineering 


condensers, bringing a heavy capacity into the 
circuit just the same. 

There is very little hand work 
Details to done on (-fog se t, and what 

Construction, must be done is quite elemen¬ 
tary, giving the experimenter 
the advantage of a splendid outfit at a small 
cost. The list of parts is helpful in getting 
together the material required. Fig. 4 gives a 
one-half scale drawing of the front panel, of 
L. P. F., 1)4. by 15 by 3/16 in. Dimensions 
can be determined by the simple method of 
setting the dividers on the drawing and doubling 
the distances. Countersunk holes are shown 
by two circles. 

The primary inductance is wound on an L.P.F. 
tube 3 y ins. outside diameter and 5 ins. long, 
with a fi-’m. wall. The first No. 27 hole for the 
coil mounting pillar is y in. from the end of the 
tube, the second % in. below, and the }4 in* 
hole for the shaft another ^ in. down. The 
winding, of No. 20 D. C. C. wire, B. and S. 
gauge, starts K in* f rom *h e center of the shaft 
hole. Taps are taken off at the left, for the 
small steps switch, at 0, 1, 2, 3, 4, 5, 6, 7, and 8, 
and on the right, for the large steps switch, at 
9, 18, 27, 36, 45, 54, 63, 72, and 81 turns. 

Taps can be made by winding extra turns, as 
has been explained in previous articles, or by the 


other side on the other outside hole, and both 
brought out through the center hole. Tap wires 
are less liable to break when taken off in this way. 



Des.by 

Tbe General ApparatusCo.lnc. % 

Or by 

150‘600mA REGENERATOR 

Cb by 

InChq. 

Piece Pt. 

Wiring Diagram 

Limits 

JobRandfl ll'ZI . 

Dec 8.19ZI 

Scale 

Dr Rni8 

SKcet 3'3 


Fig. 3. Connections for the set 

One side of the tap is cut off short, and soldered 
to the other, to make a single wire lead. 

The secondary ball is of the 3-in. standard 
size, of mahogany, wound full with one layer of 
No. 20 D. C. C. wire, B. and S. gauge. A split 



Fig. 2. Rear view, showing constructional features 


three-hole method. This is more satisfactory 
for heavy wire. Before the tube is wound, a 
set of three holes, the holes of a set spaced 
3/16 in., apart, is made for each tap. The sets 
of holes should be staggered, and spaced down 
the tube on the basis of 24 turns per inch. One 
side of the tap is put in one outside hole, the 


shaft serves as the terminals for the coil. 
Phosphor bronze springs, fastened by >^-in. 
6-32 screws to the tube at one end, and bear 
on the shaft to make contact. Lugs are fitted 
to the screws to take the connections. 

A wooden panel 6 by iy by 3 /8 ins. carries 
the socket and battery terminals. This is 




























































150 to 600 Meter Regenerative Receiver 


41 


fastened to the front panel by 1-in. 6-32 F. H. 
screws. Two 3 /8-in. holes are drilled in the base 
and 6-32 nuts put in for the screws. 

Since no mounting device is provided for the 
j Tuska variometer, four No. 27 holes are drilled 
and threaded 8-32 to take ^-in. 8-32 F. H. 
screws through the panel. They must be laid 
out carefully with a scriber and square. 


Assembly 
of the 
Parts. 


With the panel drilled, the 
coupler completed and the coil 
mounting pillars in place, the 
variometer drilled, and the tube 
base ready, the work of assembly begins. The 
switches and points are mounted, the switch 
points tinned and cleaned from paste, binding 
posts, tube base, rheostat, jack, and variometer 
put in place. Lugs should be put on the rheo¬ 
stat screws, also. It should be placed so that 
the screws will be toward the condenser end. 

Finally, the coupler goes on the panel and the 
leads are soldered. Fig. 3 gives a diagram. It 


will be noticed that on both switches and dial 
controls clockwise rotation gives an increase, 
in accordance with approved practice. 


Operation 
of the 
Receiver 


The proper use of the tuning 
controls must be learned through 
experience with the set, for the 
adjustments are so critical that, 
if not handled properly, the set will not produce 
maximum results. Adjustments should be 
made on the primary first, then the secondary 
condenser, the plate variometer, and, finally a 
slight regulation of the rheostat. Usually the 
secondary coupling is at zero. 


If an amplifier is employed, make sure that 
a 0.001 mfd. phone condenser is connected 
across the primary of the first amplifying 
transformer. Do not expect good results with 
dry cells for filament lighting. Use a storage 
battery of 6 volts, 40 or 60 ampere-hours 
capacity. 












42 


Radio and Model Engineering 


Some Common Radio Problems 


Troubles and questions that radio experimenters encounter. 


E VERY day experimenters 
wriie to the G. A. about 
Oscillate things that won t work, 

often questions that are hard to 
answer even broadly because of lack of details 
given, but there are a few common ones which 
occur so often that it may be worth while to 
take a little space to discuss them. 

The usual report is that a regenerative 
receiver doesn’t regenerate or oscillate. In 
most cases the audion filament is supplied by 
dry cells. A Radiotron UV200 or 201 will 
not work on dry batteries unless there are at 
least two sets of five cells, with the cells of a 
set wired in series and the two sets put in 
parallel. At least two sets must be used for each 
tube. 

When a circuit is oscillating the losses in the 
grid are supplied from the plate by the feed¬ 
back coupling. Unless the filament is burning 
brightly, a UV200 takes practically the full 
6 volts from a storage battery, the flow of 
current in the plate circuit is not great enough 
to supply the grid losses. Hence no oscillations. 
The plate circuit acts as a hammer hitting a 
pendulum just hard enough to keep it swinging 
steadily. 

Of course there are Radiotrons which are not 
good oscillators, but in general they are thor¬ 
oughly reliable. Remarks concerning the Radio¬ 
tron apply equally to Cunningham tubes. As 
for other makes, some experimenters like them 
and some do not. The easiest way to settle 
the tube problem is to try it in another set 
which is working. 


Very few tubes or circuits will oscillate when 
connected to an amplifier unless a condenser 
of 0.001 mfd. or more is connected across the 
primary of the first amplifying transformer. 

Another thing—a UV200 tube should have 
22.5 volts on the plate and 45 volts on the 
UV201. Voltages up to 110 can be applied to 
the latter type, however, when great ampli¬ 
fication is required. 

A variable gridleak or variable grid con¬ 
denser is not needed for regeneration. Experi¬ 
menters who have them, however, consider 
them necessary, not realizing that the adjust¬ 
ments obtained run to higher and to lower 
values than should be used. When the adjust¬ 
ments are properly set they will be found to 
be of about 1 megohm and 0.0005 mfd., the 
correct values for the gridleak and grid condenser. 


A great many electrical stores 
Phone are now se Hi n g radio receiving 

Reception sets, and some of the statements 
made by uninformed clerks 
would be amusing if they did not cause so much 
trouble for the novice who is earnestly trying 
to put up a set to receive the telephone broad¬ 
casts. I have heard clerks glibly assure custom¬ 


ers, for example, that a crystal receiver will 
bring in speech and music clearly at a distance 
of 100 miles. It won’t and doesn’t. A crystal it 
set will not give clear speech from the stations!' 1 
now transmitting when more than 10 miles 1 
away. On a good non-regenerative audion set 
readable speech can be heard over 50 miles,’, 
and 75 to 100 miles on a regenerative receiver. 1 


This is taking average results. As a matter o\ 
fact, Mr. L. M. Clement has received reports 11 * 
on the Western Electric K.W. phone station' 1 
at New York from very nearly every State in 
the Union. Reception on a loud speaker was* 
possible in California, but that cannot be done 
at every receiving station or from any other ti 
transmitting station now operating. The wave¬ 
length ordinarily used by that station is 450 c( 
meters. 


Reception 
on Loud 
Speakers 


T 


Frequently a man buys a v oca- 
loud or similar loud speaker and* 1 
complains that, altho the signals! J! 
are clear in the telephones, he 
cannot hear them two feet from the loud speaker. 
Of course not. Signals must be very strong in 
the phones before a Vocaloud can be heard in a 
large room. One to three amplifiers, with, 
pieferably, three 45-volt plate batteries on the 
last tube should be employed. Then the 
Vocaloud will make plenty of noise. These 
instruments are not meant to do the work of 
amplifiers. 


Some 

Patent 

Queries 


Then there are the questions 
about patents. Experimenters 
sometim&s get the idea that they 
want to build and sell radio in¬ 
struments, or regenerative receivers with one 
connection left off. Radio equipment and 
circuits are bound up in a net work of patents, 
some of which have been defended and some 
have not. The safest course for a man who is 
not fully informed as to conditions now existing 
and the changes that are constantly taking 
place is to take no chances, for he will not find 
the possible gain worth the risk involved. 
Neither is it safe to side-step responsibility by 
leaving out a connection or to employ similar 
methods. In the last six months many com¬ 
panies have been brought to account. In this 
connection it may be mentioned that suit has 
been brought against the Radio Service Com¬ 
pany of Lynbrook, Long Island, for infringe¬ 
ment of patents covering the familiar G. A, 
grid, phone, and gridleak condensers, though 
action is not taken in such cases frequently 
because the infringers are found to lack financia 
responsibility and have no assets against which 
claims can be made. 









Ideas for the Shop and Laboratory 


43 


Ideas For the Radio Shop and Laboratory 

lere are a few handy instruments, neatly made, which every experimenter needs 

but not so_ many have 


TlAVE you ever worked 
aborator* 6 and worked to get a res- 

isciitator^ onance point in making meas¬ 
urements with a wavemeter, 
jiving up in the end or taking a chance 
hat the readings you made were some- 
vhere near correct? You wont have to 
lo that with an oscillating wavemeter. 
The circuit is simple, and contains only 
he elements of an oscillating circuit, an 
nductance connected at one end to the 
;rid of a tube, a center tap to the fila- 
nent, and the other end running to the 
legative side of a plate battery, the posit¬ 
ive battery lead to the telephones, and 
he phones to the tube plate. A variable 
'ondenser is connected across the ends 
>f the coil. This is a laboratory oscillator 
vhich, when calibrated, becomes a wave- 

neter. . . , . 

There are many uses to which the in- 
,trument can be put described in detail 
it the end of this article. 

Tp IG. 1 shows the completed 
Construction -T meter connected and ready 
SVavemeter for use on wavelengths from 

180 to 600 meters. A uA- 
STD-A15 variable condenser, 0.0002 mfd. 
capacity, is mounted on a 5 by 5 by 3-16- 
n. panel fitted on a box 2*4 ms. deep in¬ 
side and 5 ins. square outside three 
special clamping posts are needed for con¬ 
nections, made to hold the coil connection 
lugs in the center and wires to the audion 
at the top. They are located ¥% in. from 
die edge, the left hand post being 1 5-16 
in. from the side of the panel the; next A 
in. to the right and the third 1 15-16 in. 
from the second. 

The coil is 1 7-16 in. long, of 65 turns 
of No. 24 S.S.C. wire on G-A-Lite tube 
3U ins. in diameter and 234 ins. long 
Winding is started 1 in. from the left 
hand end, and a tap is taken off at the thir 
tieth turn. Next, 1-in. round head 8-33 
screws are put thru the tube, spaced to 
line up with the binding posts and clamped 
with nuts. End and center leads from 
the coils are soldered to their respective 
screws. Finally large size soldering lugs 
are put in position on the binding posts 
and the screws on the coil soldered to 
them Thus the screws provide support 
for the coil as well as connections The 
outside binding posts are wired to the 
condenser terminals. 


Connections to the audion have been 
described already. When a Laboratory 
Type Control is employed, as in Fig. 1, 
the right hand wavemeter post is joined 
to the upper left hand control post, the 
center post to the lower control post, 
negative plate battery lead to the left 
wavemeter post, and the positive lead to 
the regular positive plate battery con¬ 
nector at the rear of the control. The 
right control panel posts take the tele¬ 
phones. 

r T'0 calibrate this meter, con- 
Calibrating X nect - t ag directed and 

Meter light the tube filament. If a 

UV200 is used, put 22.5 volts 
on the plate, or for more power a UV201 
with 45 volts. Couple the coil to the in¬ 
ductance of the calirated meter, and swing 
the condenser back and forth until clicks 
are heard in the phones. There will be 
a click on each side of the resonance 
point. Decrease the coupling until the 
clicks are very close together. The center 
point between the clicks gives the true 
reading. This method, tho it may seem 
rather uncertain from the description, 
works out very nicely in practice. 

DEFORE measuring the 
otner 1 " 11 ^ wavelength of a circuit 

Circuits disconnect any other circuit 
coupled to it or set the coup¬ 
ling at zero. Whether the circuit is for 
transmitting or receiving it is not neces¬ 
sary to excite it. Merely couple the wave- 
meter to it and listen for the clicks which 
indicate resonance. 

If the wavemeter is set up near a tele¬ 
phone or undamped wave transmitter, 
beat notes will be heard on both sides of 
the resonance point. 

T^HERE are many interest- 
^he^Uses X j ng uses f or t hi s instru- 
Wavemeter ment. It may be coupled to 
a non-oscillating audion or 
crystal circuit and used for heterodyning 
undamped wave signals. For experiments 
on impedance coupled radio frequency 
amplifiers the meter itself can be used as 
the impendance circuit. Again, it may 
be connected in the plate circuit of a non¬ 
oscillating detector, and it will cause the 
circuit to oscillate and regenerate. 











44 


Radio and Model Engineering 


TH HE only way to compare 
TeSg riSOn ^ tubes, amplifying trans- 
Switch” formers, receiving sets, and 

other devices is to connect 
one and then the other, keeping the con- 


side instead of up and down. For sim- a 
plicity, small wire was used for connec- a 
tions, insulated with Empire tubing. 

The top and side clips should be given 3 
corresponding numbers to facilitate the 



Fig-. 1, below. The complete wavemeter set-up, coupled to a receiving set. 

Fig. 2 , above. Testing switch, inductance standards, phone bob, and Inductance Tables, all 

useful things for the radio man. 


ditions the same. A handy switch for 
this purpose is shown in Fig. 2, at the 
left. 

It is a Federal anti-capacity switch 
mounted on an L.P.F. panel 5 by 5 by 
3-16 in. The panel is supported on a 
wooden base. Fahnestock clips for the 
center contacts are mounted across the 
top of the panel, and the clips on the sides 
for the side contacts. It might have been 
better to have the handle thrown to the 


wiring of instruments to be compared. 
Whatever devices are to be compared 
should be connected to the side clips, 
while the top clips go to the auxiliary 
apparatus. 

A LL kinds of experiments^ 
Inductance Call f° r inductance Stand- 

Coils ards. Every laboratory should 

have an assortment, running 
from 0.1 to 10.0 milihenries. While these 


c c c 















Ideas for the Shop and Laboratory 


are expensive in the forms in which they 
are usually manufactured, the coils in 
Fig. 2 can be wound up quickly, and to 
an accuracy of well within 5%. 

CO many times we have 
onOiJe h0neS ^ needed two pairs of phones 
Plug"* on a set provided with only 

one jack that we now use a 
phone bob. It is just a little piece of 
L.P.F. cut from a 2 x / 2 by 5 by l /& in. 
panel, carrying four Fahnestock clips, with 
a cord running to the phone plug. A 
phone bob, as we call it, is shown at the 
left of Fig. 2. Its convenience has more 
than compensated for the time it took to 
make it. 


The easiest way to determine the size 
of a coil to produce a given inductance is 
by means of ‘‘Inductance Tables.” By 
means of these Tables the size of wire, 
diameter, length, or turns per inch re¬ 
quired for a certain inductance can be 
found to an accuracy of 2% merely by 
a multiplication or division. Actually the 
Table consists of 2,900 separate calcula¬ 
tions from Nagoaka’s formula applied to 
coils from 0.1 to 10.0 ins. long and 3 
to 10 ins. in diameter but without the 
turns per inch squared value. This is 
supplied in making the calculation. A 
glance at the directions which accompany 
the Tables show how easily the required 
contents can be determined. 







46 


Radio and Model Engineering 


G. A. STANDARDIZED PARTS FOR THE 
SINGLE CIRCUIT RECEIVER 


1—L. P. F. Panel 10x5x 3 ,4 in. for front. 

1— L. P. F. Panel 1-5x2 y 2 x s /(o in. 

6—Switch points, 4j£ .. 

2— Stopping points, 51 .. 

1—G. A. grid leak condenser. 

1—G. A. Knob and dial, 180 degrees... 

1—Rear panel support rod. 

8—STD nickel plated binding posts, 10 ^ ea.. . 

1—G. A. audion socket.. .. 

1—G. A. rheostat.. 

1—Brass strip %xVfe in*, P er ft. 

1—-Closed circuit Federal jack. 

1—GA-STD variable condenser, 0.0008 mfd. . . 

1— Package of No. 6 soldering lugs. 

2— Coil supporting pillars, 8^ ea. 

1—V 2 lb. spool No. 24 S. S. C. wire. 

1—3 in., G-A-Lite tube 12 in. long. 

1—Package 6-32 V 2 in. R. H. brass screws . 

1—Package 6-32 x / 2 in. F. H. nickeled screws.. 
1—Package 6-32 1 in. F. H. nickeled screws. . 

3— 24 in. length square tinned copper wire.. . 
Complete set of parts to construct this re¬ 
ceiver as listed above, can be assembled, 
with the simplest tools in a few hours. . 


$1.31 

.24 

.24 

.10 

.50 

1.25 

.11 

.80 

.80 

1.15 

.13 

.85 

4.30 

.25 

.16 

1.25 

.32 

.12 

.12 

.14 

.18 


13.99 


AUXILIARY EQUIPMENT 


Radiotron U. V. 200 detector tube. $5.00 

Radiotron U. V. 201 amplifier tube. 6.50 

B battery, 22.5 volts. 1.75 

Witherbee storage battery, 40 A. H. 6V. 14.00 

Federal telephone plug. 1.75 

Inductance, wound and tapped as shown. 3.00 

Front panel fully engraved, extra. 2.50 

Rear panel fully engraved, extra. 2.10 


PARTS^FOR 150 TO 1,000 AND 150 TO 2,500 
METER LOOSE COUPLERS 

1—L. P. F. panel 5xl0x 3 4in., for front.. ( y 2 lb.) $1.31 

1—L. P. F. panel 2 x / 2 x5x Vs in., for rear. . (3 oz.) .24 

3— Switch 1 in., radius 65^.(2 oz.) 1.95 

4— Pillars to mount coils 8^ ea.(2 oz.) .32 

1—G. A. 90 degree dial and knob.(2 oz.) 1.25 

1—Rear panel support rod 3 /f 6 in. sq.. . . (3 oz.) .11 

28—Switcn points, 4 £ ea. .72 

1 —14 in., brass rod, per 12 in. length. . (4 oz.) .15 

1— 3 in., mahogany variometer ball.... (3 oz.) .90 

4—GA-STD nickel plated binding posts 

10^ ea.(2 oz.) .40 

2— -Square copper connection wire, 6(4 

per 2-ft. length. .12 

1—Piece No. 24 spring sheet brass 5x6 

in.(3 oz.) .27 

1—Short wave primary coil, wound and 

tapped.(8 oz.) 1.00 

1—Short wave secondary coil wound 

and tapped.(8 lbs.) .85 

1—Long wave primary coil wound and 

tapped.(lib.) 2.20 

1—Long wave secondary coil wound and 

tapped.(8 oz.) 1.35 

1—Package of 6-32 y 2 -in. R. H. nickel 

brass machine screws.(1 oz.) .12 

1—Package 6-32 1-in. F. H. nickeled.. .(2 oz.) .14 
Complete set of parts for the 150 to 1,000 
meter loose coupler as listed above, 

ready to assemble.(3 lbs.) 8.95 

Complete set of parts for the 150 to 2,500- 
meter coupler, as listed above, 
ready to assemble.(4 lbs.) 10.90 


AUXILIARY PARTS 

V 2 lb. spool No. 24, single silk covered 

wire 400 ft. $1.25 

9-in. length G-A-Lite tubing 3 l / 2 in. 

diameter.(8 oz.) .38 

GA-STD variable condenser, 0.0008'mfd.(l lb.) 4.30 
L. P. F. panel 5x5x 3 /{ 6 in. for mounting 

condenser.(6[oz.) .67 

G. A. 180° dial and knob.(2 oz.) 1.25 


STANDARDIZED, PARTS FOR THE ICO TO 
2 , 6 C 0 METER REGENERATOR 

1—L. P. F. panel 5xl0x 3 .4 in.(12 oz.) $1.31 

1 —L. P. F. rear panel 2 y 2 xl0xy s in.(4 oz.) .45 

4—Lengths % in. angle brass.(3 oz.) !80 

GA variable condenser 0.0008 mfd. (1 lb.) 4*30 

1—180° dial and knob l / 4 in. hole. (2 oz.) 1.25 

1—90° dial and knob l / 4 in. hole.(2 oz.) 1.25 

1—Complete switch, 1 in. radius.(2 oz.) !fi5 

10—Switch points. (1 oz.) !40 

1 —G-A-Lite tube 3 V 2 in. diam. (5 oz.) .38 

1—V 2 lb. spool No 24 S. S. C. wire.... (8 oz.) 1.25 

3—Coil supporting pillars.(2 oz.) .24 

1— Length y 4 in. brass rod.(7 oz.) .15 

2- ft. Empire tubing. (2 oz.) .40 

1— Pkg. 6-32 washers.(1 oz.) .04 

2— Pkg. y 2 in. 6-32 R.H. nickeled screws(l oz.) .24 

2—Pkg. 6-32 nickeled nuts. (1 oz.) .16 

1—Pkg. V4in.4-36R.H.nickeled screws (l Q z.) .11 

1— Pkg. 1/4 in. 4-36 nickeled nuts.(1 oz.) .08 

6—GA-STD nickeled binding posts.(3 oz.) .60 

2— Lengths square tinned copper con¬ 

nection wire. (2 oz.) .12 

1—GA-STD mahogany variometer bali, 

shaft hole drilled. (3 Q z.) .90 

Complete set of parts to build the 150-to- 

2,600 meter regenerator.(7 lbsj 14.87 

NOTE—This set, giving extremely loud signals on 
phone signals, costs less than two variometers 
alone. 


AUXILIARY PARTS 

Complete supporting frames, nickeled pair (6 oz ) $1 25 

Inductance coil wound and tapped.. 4*00 

Complete inductance unit with coupling 

coil, ready to mount on panel . c 95 

Front panel with condenser, coil, and 
tickler mounted, fitted with dials, 
switch, and switch points, practi¬ 
cally finished except for supports, 

connection panel and wiring.. 17 02 

Complete set of parts, including nickeled 
frames, panels drilled and en¬ 
graved, and both coils wound. (7 lb.) 19 88 

STANDARDIZED PARTS FOR THE DETECTOR 
AND TWO-STEP AMPLIFIER 

2 L. P. F. panels 5xl0x 3 /f 6 in. (24 oz ) «9 no 

P -I- r s“ e ™* 12 V xl °'/»i»-- •: “ oi\ * 2 1 

4—Lengths % in. angle brass... (8 oz ) 80 

6 —Lengths square tinned copper wire (4 oz) 

l~r' 1 * t rheos f tats .(16 oz! 3:45 

2—G. A. transformers. (16 oz i in nn 

2 — Federal closed circuit jacks.. (6 oz) 17 * 

cir £H* *<*. 

3— GA-STD-A 1 sockets. fio m 'i o in 

10 GA-STD-A 10 binding posts.' .'.*,* * * (5 oz * ? IS 

1 —Pkg. small soldering lugs.. J °z* 1 * 2 ® 

^ g * S’ 6-32 % scr ews nickeled (2 oz! *24 
J P^g. R. H. 6-32 y 2 in.screwsnickeled(l oz‘) 12 
J-g*- 4 ’ 36 1/2 * n * screws nickeled (1 oz *}? 

3—Pkg. 6-32 nuts, nickeled... ro nz \ 

1—Pkg. 4-36 nuts, nickeled..J £z* ns 

i—GA-STD-A4 grid leak condenser... . 1 0 z! '50 

Complete set of parts as listed above 7 ' ou 
ready to assemble in your own 

Sh0p ' : .. . 24.82 

SEMI-FINISHED, PARTS 

Front panel drilled, extra. _ 

Bottom panel drilled, extra. ... . qj! 

Rear panel drilled, extra.. . 

Complete support frames, nickeied,' per pr! " " 1 

Drilling all panels and mounting all parts readv 

to wire, extra. y . . 

Complete set of parts in the panels drilled. 

and engraved and nickeled support 

frameS .. lbs.) 29.90 


auxiliary parts 

GA. standardized B battery 45 volts, 

22 y 2 - volt top. f ’ 3 ,, . 

Witherbee 6-volts, 40-amp-hour storage J 

battery. & ( , h 

Radiotron detector tube, UV 200. 

Radiotron amplifier tube, UV 201. ra 

Federal telephone plug.. . 4 % 


$3.20 

14.00 

5.00 

6.50 

1.75 
























































































List of Parts and Prices for Instruments Described 


47 


STANDARDIZED PARTS FOR THE SINGLE 
CIRCUIT CRYSTAL RECEIVER 


i p - F - P an el 5x5x 3 /f 6 in.(6 oz.) $0.67 

~ G-A-Lite tube 3-in. diam.(5 oz.) .32 

[ ?- 14 lb- spool No. 24 S. S. C. wire.... (5 oz.) .70 

* GA-STD-A13 switch points.(1 oz.) .40 

10—Switch complete .(2 oz.) .65 

1 Coil mounting pillars.(3 oz.) .16 

2—Detector parts.(3 oz.) .75 

1 Mounting galena crystal... (1 oz.) .30 

1 GA-STD-A10 binding posts.(4 oz.) .40 

; 4—Brass strip 3/gxi^g i n .(3 oz.) .13 

2 Length sq. tinned cop. wire.(2 oz.) .12 


4 Pkg- F-H6-32 V 2 in. screws nickeled(2 oz.) .12 

1 Pkg. 6-32 y 4 in. screws nickeled... . (1 oz.) .11 

1 Pkg. 6-32 nuts nickeled.(1 oz.) .08 

1—Pkg. No. 6 washers.(1 oz.) .04 

1—GA-STD-A3 phone condenser.(1 oz.) .35 


COMPLETE SET OF PARTS 

As listed above ready to assemble in your 

own shop.(4 lbs.) $4.92 


AUXILIARY PARTS 

GA-STD-A11 plate battery, 22 Vi volts.. . (2 lbs.) $1.75 

Radiotron UV200.(8 oz.) 5.00 

Witherbee 6-volt, 40 ampere-hour storage 

battery.(15 lbs.) 14.00 

GA-STD-A6 amplifier control.(2 lbs.) 13.95 

Radiotron UV201.(8 oz.) 6.50 


STANDARDIZED PARTS FOR THE 
OSCILLATING WAVEMETER 

L. P. F. panel 5x5x 3 /f 6 ins.(6 oz.) $ .67 

Knob and dial.(2 oz.) 1.25 

GA-STD-A18 double base binding 

posts.(3 oz.) .42 

Length G-A-Lite tube, 3 Vi in. diam.. (7 oz.) .38 

Vi lb. spool No. 24 S. S. C. wire-(6 oz.) .70 

Pkg. large soldering lugs.(3 oz.) .31 

GA-STD-A15 0.00025 mfd, condens- 

per.(10 oz.) 3.25 

Pkg. 8-32 1 in. R. H. nickeled screws (2 oz.) .16 

Cabinet.(lib.) 2.00 

Pkg. 8-32 Vi in. nickeled screws... . (1 oz.) .14 


1 — 

1 — 

3 

1 — 

1— 

1 — 

1 — 

1 — 

1 — 

1 — 


,SEMI-FINISHED PARTS 

j Front panel drilled, extra. $ .50 

Coil wound and tapped, complete.(10 oz.) 1.00 

Panel, switch, switch points and coil 

mounted with taps soldered.(2 lbs.) 5.30 


AUXILIARY PARTS 

An enna wire, No. 14 bare copper, per 

100 ft.(2 lbs.) $ .94 

3-in. HF insulators, 33,000 volts, 350 lbs.. (6 oz.) .25 
Mvrrdock phones, 2,000 ohms, with head- 

band.(lib.) 5.00 


STANDARDIZED PARTS FOR 200-METER 
RECEIVER WITH RADIO FREQUENCY 

v n > / n 11 

1 —L. P. F. panel 10x7 y 2 x 3 /f 6 in.(20 oz.) $1.97 

1— L. P. F. rear panel 10x2 y 2 x y 8 in.(4 oz.) .45 

s — Lengths % in. angle brass...(12 oz.) 1.20 

4— Lengths tinned square copper wire.. (3 oz.) .24 

2— G. A. rheostats.(8 oz.) 2.30 

2— GA-STD-A1 sockets.(8 oz.) 1.60 

8— GA-STD-A10 binding posts.(4 oz.) .80 

1— Pkg. small soldering lugs.(1 oz.) .25 

2— -GA-STD-A18 variable condensers. (2 lbs.) 8.60 

1 — GA-STD-A2 grid condenser.(1 oz.) .35 

3— Knobs and dials, 180°.(6 oz.) 3.75 

' L — GA-STD-11 mahogany tickler ball. .(3 oz.) .90 

1 —G-A-Lite tube 3 Vi ins. diam.(5 oz.) .38 

1— V 2 lb. spool No. 20 D. C. C. wire.. . (10 oz.) .80 

1— Length V4 in. brass rod.(7 oz.) .15 

2— Lengths s/gx 1 /^ in. brass strip.(12 oz.) .26 

2— Pkg. V 2 . in. 6-32 F.H. nickeled screws. (2 oz.) .24 

1 —Pkg. Vi in. 8-32 F.H. nickeled screws. (1 oz.) .14 

1— pkg. 1 in. 8-32 R. H. nickeled screws.(1 oz.) .16 

1— Pkg. Vi in. 4-36 R.H. nickeled screws. (2 oz.) .11 

1 -Pkg. Vi in. 6-32 R. H. polished nick¬ 


eled screws.(1 oz.) .12 

2—Nickeled coil mounting pillars.(2 oz.) .16 

4 —Brass washers V4 in. hole.(2 oz.) .04 

1—Pkg. No. 6 nickeled washers.(1 oz.) .04 

1—Pkg. 4-36 nickeled nuts.(1 oz.) .08 

1—Pkg. 6-32 nickeled nuts.(1 oz.) .08 

1—Pkg. 8-32 nickeled nuts.(1 oz.) .09 


STANDARDIZED PARTS FOR IN¬ 
DUCTANCE STANDARDS 

Inductance tables, post paid. $0.25 

G-A-Lite tubing, 3 in. diam., 9 in. length. (5 oz.) .32 

G-A-Lite tubing, 3 y 2 in. diam., 9 in length(7 oz.) .38 

G-A-Lite tubing, 4y 2 in. diam., 9 in. Igth. . (9 oz.) .48 

No. 24 S. S. C. wire, per y. lb. spool ... (6 oz.) .70 

No. 24 S. S. C. wire, per 1 lb. spool.(18 oz.) 2.25 


STANDARDIZED PARTS FOR PHONE BOB 

Federal phone plug.(5 oz.) $1.75 

Nickeled Fahnestock clip.(1 oz.) .03 

L. P. F. Panel 2 y 2 x5x 3 ,4 in.(3 oz.) .34 


STANDARDIZED PARTS FOR THE 12,000 TO 
20,000 METER RECEIVER 


1—L. P. F. panel 10x7y 2 x 3 /i6 in.(1 lb.) 

1— L. P. F. panel 10x2 y 2 xy 8 in.(8 oz.) 

2— 24 in. lengths square tinned copper 

wire.(2 oz.) 

6—12 in. lengths % in.angle brass.... (12 oz.) 

6—GA-STD-A10 binding posts.(3 oz.) 

1—Pkg. of 20 small soldering lugs.(1 oz.) 

1—GA-STD-A7 180° dial and knob.(8 oz.) 

3— Lb. No. 24 S. S. C. copper wire. ... (3 lbs.) 

1— GA-STD-13 indicating knob, % in. 

hole.(2 oz.) 

2— 12 in. lengths %xVf6 in. brass strip.. (12 oz.) 

2—12 in. lengths in. brass rod.(8 oz.) 

10—GA-STD-8 threaded posts..(6 oz.) 

4 — GA-STD-14 coil mounting pillars.. . (5 oz.) 

1—GA-STD-A17 variable condenser.. . (1 lb.) 
1 —9 in. length 3 Vi in. G-A-Lite tube... (6 oz.) 
1 —9 in. length 4*4 in. G-A-Lite tube... (9 oz.) 
1—Pkg. of 10 screws 6-32 V 4 in. F. H...(l oz.) 

1—Pkg. of 10 screws 6-32 Vi ; in. F. H...(2 oz.) 

1— Pkg. of 10 screws 6-32 1 in. F. H.... (4 oz.) 

2— Pkg. of 10 nuts 6-32.(2 oz.) 

1—Pkg. of 10 screws 6-32 Vi in. R. H..(l oz.) 

1— Pkg. of 10 screws 8-32 Vi in. F. H...(3 oz.) 

2— 12 in. length flexible conductor.(1 oz.) 


$1.95 

.47 

.12 

1.20 

.60 

.25 

1.25 

6.75 

.40 

.26 

.18 

.40 

.32 

4.30 

.38 

.46 

.11 

.12 

.14 

.16 

.11 

.14 

.08 


COMPLETE SET OF PARTS 


COMPLETE SET OF PARTS FOR THE 
RECEIVER 


As listed above ready to assemble in your 
own shop. The cost of the complete 
set is less than that of two vario¬ 
meters and a varicoupler.(8 lbs.) $25.46 


As listed above, ready to assemble, more 
efficient and less expensive than 
concentrated coil receivers.(8 lbs.) $19.89 


SEMI-FINISHED PARTS 


Front panel drilled, extra. 

Rear panel drilled, extra.. 

Complete supporting frames, nickeled, 

per pair.(12 oz.) 

Coil and tickler assembled with leads 

soldered ready to mount..._.(1 lb.) 

Complete set of parts, including nickeled 
support frames, panels drilled and 
engraved..lbs.) 


$ .90 
.40 

1.70 

3.89 

29.68 


SEMI-FINISHED PARTS 


Front panel drilled and slotted extra . 

Rear panel drilled, extra . 

Antenna inductance wound . (3 lbs.) 

Tickler inductance wound . (2 lbs.) 

Complete nickeled support frames, per 

pair . (12 oz.) 

Complete set of parts, including nickeled 
support frames, all panels drilled 
and engraved, coils wound . (8 lbs.) 


$0.90 

.30 

5.00 

4.50 

1.50 


26.15 






















































































48 


Radio and Model Engineering 


AUXILIARY APPARATUS 

GA-STD-A5 Laboratory type detector 

control.(lib.) $5.95 

GA-STD-A6 Laboratory type amplifier 

control.(2 lbs.) 13.95 

GA-STD-A3 Phone condenser, 0.001 mfd.(2 oz.) .35 

Radiotron UV200 detector tube.(8 oz.) 5.00 

Radiotron UV201 amplifier tube.(8 oz.) 6.50 

GA-STD-A11 plate battery 22 V 2 volts...(2 lbs.) 1.75 

GA-STD-A12 plate battery 45 volts, 22 V 2 

volt tap.(4 lbs.) 3.20 

Witherbee 6-volt, 40-ampere-hour, stor¬ 
age ^battery charged and ready to 
use.(15 lbs.) 14.00 


STANDARDIZED PARTS FOR THE 150 TO 
600-METER REGENERATIVE RECEIVER 

l—GA-STD-8 P L. P. F. panel 15x7 V 2 x 

% in.(1 y 2 lbs.) $2.97 

1—12 in. length Vi in. brass rod.(7 oz.) .15 

1— Wooden base 6x2 V 2 X % in.(5 oz.) .20 

2— GA-STD-A7 100 division dial and 

knob Vi bi. hole.(lVilbs.) 2.50 

1— GA-STD-A8 50 division dial and 

knob Vi in. hole.(9 oz.) 1.25 

2— GA-STD-A9 1 in. radius switch-(10 oz.) 1.30 

1—G. A. rheostat.(6 oz.) 1.15 

18—GA-STD-A13 switch points.(2 oz.) .72 

4—GA-STD-A10 binding posts. (10 oz.) .40 

1— Federal open circuit jack.(6 oz.) .70 

2— 2 ft. lengths Empire tubing.(2 oz.) .80 

1— Pkg. of 20 small soldering lugs.(2 oz.) .25 

2— Coil mounting pillars.(3 oz.) .16 

1—Pkg. of 20 No. 6 nickeled washers..(1 oz.) .04 

1—Pkg. of 10 y 2 in. 8-32 F. H. nickeled 

screws.(2 oz.) .14 


3— Special Fahnestock binding posts..,. (1 oz.) $.12 

1— GA-STD-A4 grid leak condenser... . (2 oz.) .50 

2— Rotor shaft contact springs.(1 oz.) .08 

2—Fiber rotor spacing washers.(1 oz.) .08 

1—Pkg. of 10 V4 in. 6-32 R. H. nickeled 

screws.(3 oz.) .11 

1 / 2 —lb. No. 20 D. C. C. wire.(8 oz.) .80 

1—GA-STD-A1 audion socket.(5 oz.) .80 

1—Pkg. of 10 6-32 nickeled nuts.(2 oz.) .08 

1—GA-STD-11 mahogany coupling ball. (5 oz.) .90 

1—GA-STD-A17 0.001 mfd. variable 

condenser.(lib.) 4.30 

1—Tuska Variometer.(2 lbs.) 6.25 

1—L. P. F. tube 5 in. long 3 V 2 i n - diam. 

Vs in. wall.(6 oz.) 1.48 

4— 2 ft. lengths square tinned copper 

wire.(2 oz.) .24 

4—Stopping points.(2 oz.) .20 


complete set of parts for receiver 

As listed above ready to assemble.(10 lbs.) $29.97 


SEMI-FINISHED PARTS 

Panel drilled, extra. $1.10 

Varicoupler wound and assembled.(2 lbs.) 5.95 

Set of parts, including wound varicoupler 

panel drilled and engraved.(10~lbs.) 33.99 


AUXILIARY PARTS 

GA-STD-A6 laboratory type amplifier 

control.(2 lbs.) $13.95 

UV200 radiotron detector tube.(8 oz.) 5.00 

UV210 radiotron amplifier tube.(8 oz.) 6.50 

Murdock 2,000-ohm phones.(1 1 / 2 lbs.) 5.00 


NOTE: 

These supplies can be purchased prom G.A. Dealers. Only orders to be filled by 
mail are accepted by the G.A. Company at 88 Park Place, N. Y. C. Special retail 
department at Wortheimer's, 181st Street between St. Nicholas and Wadsworth Anjenues. 

'Take the Broadway Subway to 191st Street. 


Radio and Model Engineering 

Edited by M. B. Sleeper 


Radio and Model Engineering is a monthly maga¬ 
zine devoted exclusively to the construction of radio 
apparatus which can be built in the “kitchen table 
workshop’' from parts readily obtainable. 

You can get an idea of R. and M. from this book, the 
pages of which are reprinted from previous issues. 
You ought not to miss the coming numbers. A single 
article may be worth a year’s subscription. 

Put a dollar bill, with your name and address, in an 
envelope and send it to the G. A. Company. You 
will find it the best investment you ever made. 

The General Apparatus Co., Inc. 

88-B Park Place, New York 
















































